|   | DATA MINING Desktop Survival Guide by Graham Williams |   | |||
| Recenter | 
A common normalisation is to recenter and rescale our data. The
simplest approach to do this is to subtract the mean value of a
variable from each observation's value of the variable (to recenter the
variable) and to then divide the values by the root-mean-square of the
variable values (
 ), which re-scales the
variable back to a range within a few integer values around zero.
), which re-scales the
variable back to a range within a few integer values around zero.
Rattle relies on the scale function from the base package to perform the re-centering:
| > weather$RRC_Evaporation <- scale(weather$Evaporation)[,1] > summary(weather$RRC_Evapration) | 
| 
Length  Class   Mode 
     0   NULL   NULL
 | 
Note that the resulting mean is not precisely zero, but pretty close.